1. Field of the Invention
This invention relates to alkyl and haloalkyl N,N'-dialkyl-N-methylolphosphorodiamidates.
2. Description of the Prior Art
Phosphorus-containing compounds are well known for their ability to impart flame resistance to fabrics. Many of such prior art compounds may be undesirable as flame retardants for fabrics because they stiffen the fabric, because of their volatility which leads to their loss, at least partially, during any curing operation, because of their toxicity, because they must be employed in large quantities to impart any significant flame resistance to the fabric, or because they are not fast to laundering. Known flame retardants for fabrics include phosphorodiamidates. Such materials usually are employed in combination with aminoplast resin precondensates to achieve durability or fastness to laundering. If the amount of aminoplast required is high, excessive and intolerable stiffening of the fabric may result.
British Pat. No. 799,606 discloses that textile fabrics can be made flame resistant with N-methylol derivatives of alkyl or aryl esters of phosphorodiamidic acid, the alkyl or aryl group optionally being substituted with, for example, halogen. Preferably, the diamidic acid derivative is employed in combination with an amino-aldehyde resin. Such diamidic acid compounds may be undesirable because they impart objectionable stiffness to the fabric, because they cannot be made up into storage stable solutions, because the washfastness of the flame resistance imparted to the fabric decreases with increasing age of the solution before application, or because the flame resistance imparted to the fabric is not durable to home bleaching. Moreover, such diamidates may be undesirably expensive, in pure form, if they are prepared from a phosphoryl chloride, an alcohol and ammonia, yielding the difficulty separable ammonium chloride as a by-product.
U.S. Pat. No. 2,828,228 discloses the use of alkyl and haloalkyl phosphorodiamidates and monoamidates, with or without N-alkyl substituents, in combination with a methylolmelamine for rendering cellulosic fibers flame resistant. Such flame retardants may impart undesirable stiffness to the cellulosic fibers. Similar amidates are disclosed in British Pat. No. 790,663 for imparting flame resistance to cellulosic materials.
British Pat. No. 1,222,885 discloses as flame retardants for cellulosic materials, compounds or combinations of compounds which contain nitrogen and phosphorus. It further discloses that fabrics treated with such a compound or combination of compounds have a good degree of flame retardance if the nitrogen content is equal to or greater than 6% minus 4 times the phosphorus content and, preferably, is at least 2.5 times the phosphorus content, with the preferred amounts of nitrogen and phosphorus totaling at least 3.5%, based on the weight of fabric. Exemplary of compounds containing both nitrogen and phosphorus are phosphorodiamidates having the formula ##EQU1## wherein R can be substituted or unsubstituted C.sub.1-6 alkyl.
U.S. Pat. No. 2,832,745 discloses the use of phosphorodiamidates in combination with an adduct of a polymerizable phosphate ester and a polymethylol amide, azine or azole for imparting flame resistance to flammable materials, and U.S. Pat. No. 2,971,929 discloses a five-component mixture for imparting flame resistance and water repellency to combustible materials, which mixture can include an alkyl N,N'-dialkylphosphorodiamidate.
German Pat. No. 1,009,629 discloses flame retarding phosphorus compounds which are obtained by treating phosphoric triamide with formaldehyde and methanol. The product, which includes phosphorus esters and hexamethylenetetramine, appears to lack durability to laundering.